It may sound like a scam, but it's actually pretty legit. Clever "rewards travelers" have figured out a way to get airline miles by purchasing money, because the U.S. Mint sells $1 Presidential Coins, at cost and by the roll. Since the Mint also offers free shipping for orders over $500 (coins are heavy), some have even managed to get huge amounts of miles for what technically equals zero dollars spent.

So, considering the average frequent flyer mileage runs at about two miles for every dollar spent, you could get a quick 100 miles added to your account by just ordering two $25 rolls of actual money. Since the Mint sells these coins all year long, every year since 2007, there's no rush to do it all at once, either.

The only catch is that the Mint doesn't want people to immediately deposit the dollar coins into their bank accounts, they want the money to circulate. The idea is for the coins to be used in stores, on buses, at food trucks—basically anywhere that would get them out and moving. So, while nobody would stop you from depositing rolls of coins at the bank, you can bypass any feelings of guilt by using them to buy things instead. Photo by Roger Schultz.